In one embodiment of the present invention, a shock absorber or dampener is provided which uses a drive to adjustably control the effective axial length of the shock in order to accommodate a plurality of seat heights. The length of the shock is adjusted by providing threads on a rod that forms part of the shock assembly which coact with threads associated with the drive source. The operation of the drive and subsequent coaction between the threads causes the rod to thread axially changing the effective length of the rod and the overall length of the shock.
In another embodiment of the present invention, an actuator is further provided with the device. The actuator moves axially in conjunction with the rod and is used to adjust the height of a seat suspension. As the actuator moves axially, it operates a valve that controls air flow into and out of the air spring. The actuator causes air to flow into the spring to increase the seat height and exhausts air to decrease the seat height.